Leo Sartori

There is no shortage of books on relativity. The two I have on my
shelves illustrate the range: Calder's Einstein's Universe is a broad
"layman's guide" to relativity in which nary an equation is to be
found, while Misner, Thorne, and Wheeler's Gravitation has enough
mathematics to satisfy anyone. And there are hundreds of volumes
between these extremes: is there a niche for Understanding
Relativity?.

Understanding Relativity is a textbook — the exercises at the end of
each chapter are a giveaway — but one that is close in many ways to works
of popular science. It doesn't shy from equations or mathematics, but it
assumes only basic algebra and trigonometry, an understanding of what a
vector is, and simple mechanics — no calculus and no electromagnetism.
It begins with Galilean relativity and the Michelson-Morley experiment,
then presents the basic postulates of relativity, Lorentz transformations,
space time diagrams (including Loedel diagrams, which were new to me),
and some of the standard "paradoxes". This is all explained clearly,
with expansive explanations which avoid repetition. A brief account of
relativistic mechanics (simple collision problems, the energy-momentum
4-vector) and chapters on general relativity and cosmology follow.

It's not easy to put myself in the shoes of someone encountering
relativity for the first time. I think, however, that Sartori's
account would work well for anyone with the appropriate background. It
has the simplicity and readability I associate with the best popular
science, combined with just enough quantitative mathematics and logical
rigor — enough to give it a depth that would otherwise be impossible,
but not so much as to obscure the basic ideas. Understanding
Relativity would be suitable for a university course aimed at
non-physics majors — with its good treatment of the historical
background, students studying history and philosophy of science are one
obvious audience. It is also within the reach of bright high school
students or anyone else with equivalent mathematics and physics.